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Biomedical subjects

V Kumar

Publications and source records attributed to V Kumar.

At least 451 records · Page 25Linked to original sources
PubMed1992

Synthesis and substance P receptor binding activity of androstano[3,2-b]pyrimido[1,2-a]benzimidazoles.

Several heterosteroids containing a dihydroethisterone skeleton were prepared and shown to displace substance P in a receptor binding assay. Further biochemical (kinetic and Scatchard analyses) and pharmacological evaluation (substance P-induced plasma extravasation and salivation in the rat) of a representative example in this series (5a) established that these compounds are competitive antagonists at the substance P receptor.

Androstanes↗
PubMed1992

Hepatitis B virus envelope epitopes: gene assembly and expression in Escherichia coli of an immunologically reactive novel multiple-epitope polypeptide 1 (MEP-1).

A novel synthetic 323-bp gene with the open reading frame of a multiple-epitope polypeptide has been assembled and cloned. The gene is engineered by contiguous alignment of selected epitopes and functional domains of the hepatitis B virus envelope proteins separated by pairs of glycine residues. High-level bacterial production of this 100-amino acid (approx. 10 kDa) protein has been achieved and the gene product is stable. ELISA and Western blot experiments using epitope-specific antisera confirm that the corresponding epitopes are present in the engineered protein.

Amino Acid Sequence↗
PubMed1992

Subjugation of dominant immunogenic determinants within a chimeric peptide.

The mechanism of immunodominance was investigated using chimeric peptides from mouse myelin basic protein consisting of the immunodominant I-Au-restricted Ac1-11, attached by a peptide bond to I-Eu-restricted 35-47. Our results indicate that this chimeric peptide and certain of its derivatives were excellent immunogens both in vitro and in vivo. Notably, on immunization with Ac1-11:35-47 or Ac1-11 (Ala4):35-47, the proliferative T cell responses to each of its component peptides were almost completely "subjugated" in favor of neo-determinants that are I-Eu restricted. Furthermore, each of 11 hybridomas derived after immunization with Ac1-11:35-47 had specificity for junctional neo-determinants and none could be stimulated to produce interleukin-2 from Ac1-11 or 35-47. Subjugation of the immunogenicity of the original determinants occurred regardless of their dominance when separate. It did not appear to result from non-availability of the original determinants because the chimeric peptide was able to induce neonatal tolerance to each of its constituents. These results indicate that in an overlapping multideterminant array, the dominant determinant is unpredictable from historical data about any of the components. Determinant choice, at any stage of processing, may be governed by competitive aspects of determinant capture in an environment where all components--antigen, major histocompatibility complex and T cell receptor--are available.

Amino Acid Sequence↗
PubMed1992

Measurement of femoral torsion with ultrasound: evaluation of a new technique using reference lines on the posterior surface of the femur.

A technique of measuring femoral torsion employing reference lines on the posterior surface of the femur has been described. This technique was evaluated on 27 dry adult femora and then on 40 adult patients. The technique was found to be reliable and reproducible. The values of femoral torsion obtained by this technique is lower than that obtained when anterior reference lines are used.

Adult↗
PubMed1992

Circadian nature of the photoperiodic clock in Japanese quail.

The photoperiodic clock in quail (Coturnix coturnix japonica) is based upon a rhythm of photoinducibility (phi i) but the extent to which this rhythm is circadian remains unclear. Two types of experiment investigated this situation. In the first, gonadectomized quail were adapted to live in periods of darkness by training them on a schedule containing one short day and 3 days of darkness (SD/DD/DD/DD). They were then exposed to a single pulse of 6 or 10 h of light at different times across 3 days of darkness. The photoperiodic response, measured by the increase in LH secretion, showed clear rhythmicity, demonstrating unequivocally the circadian nature of phi i. The second set of experiments employed Nanda-Hamner cycles and varied the length of the photoperiod from 6 to 11 h. Responsiveness in a 36 h or a 60 h cycle was highly dependent upon the length of the photoperiod, something not predicted from theory. For instance, LD 6:30 was not photoperiodically inductive but LD 10:26 was clearly inductive. Close analysis of patterns of LH secretion indicated an unexpected delay before induction occurred and then a rapid rise to a stable level of induction. When LH was measured in every pulse under LD 10:26 there was no evidence that LH levels alternately increased and decreased. This is not consistent with the simplest interpretation of Nanda-Hamner experiments where alternate pulses of light are thought to "entrain" the rhythm or "induce" a photoperiodic response by coinciding with phi i. It is concluded that the quail's photoinducible rhythm is indeed based on a circadian rhythm but one that is only weakly self-sustaining.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Experimental infection of pigs with a Taenia species from Korea: parasitological and serological aspects.

Belgian Landrace piglets were experimentally infected with eggs of a Taenia sp. of Korean origin. At autopsy, metacestodes were present only in the livers. The proportion of degenerated metacestodes increased from 12%-39% at 5 weeks to 94%-100% at 10 weeks after infection. A sandwich enzyme-linked immunosorbent assay (ELISA) using monoclonal antibodies raised against the excretory-secretory products of T. saginata metacestodes detected circulating antigen in the sera of the pigs at 1 week post-infection. A good correlation was found between the presence of viable metacestodes and the detection of circulating antigen; the latter disappeared as the metacestodes died off. However, the antibodies were detected only after 3 weeks of infection and onwards until the necropsy of the pigs.

Animals↗
PubMed1992

A monoclonal antibody-based ELISA for the detection of circulating excretory-secretory antigens in Taenia saginata cysticercosis.

A series of monoclonal antibodies (MoAb) produced against excretory and secretory products from 10- and 20-week-old Taenia saginata cysticerci were tested for their ability to detect circulating antigen in a double antibody sandwich enzyme-linked immunosorbent assay (ELISA). Two MoAb, 12G5 and 2H8, proved to be highly reactive with the tegument of viable T. saginata cysticerci and recognized antigenic components of 65, 87 and 100 kDa in immunoblotting. The detection limit of the assay using 12G5 as trapping antibody and 2H8 as a biotinylated indicator antibody was 0.1 ng protein per ml. Although the sensitivity of the test varied from one animal to another, the minimum number of living cysticerci, which could be detected by the ELISA, was 88. Animals harbouring only dead cysticerci gave similar reactions as non-infected control animals. Cross-reactions were only observed with taeniid parasites. The test was able to detect circulating antigen also in sheep and pigs, respectively infected with T. ovis and T. solium and in the serum samples of confirmed cases of human T. solium cysticercosis.

Animals↗
PubMed1992

Photostimulation of blackheaded bunting: subjective interpretation of day and night depends upon both photophase contrast and light intensity.

Blackheaded buntings were exposed to constant dim light (approximately 2 lux) for 77 days and subsequently to 12:12 illumination, consisting of either dim light:complete darkness (dl:dk) (2:0 lux) or bright light:dim light (bl:dl) (10, 35, and 90 lux:2, 10, and 35 lux, respectively, with 180 degrees bl:dl transitions) for 2-3 weeks each. Birds were unstimulated until day 100, under dim LL (dl:dl) and 12dl:12dk. Photostimulation with a significant increase (p less than 0.001) in average body weight and testis volume occurred on exposure to 12bl:12dl (10:2 lux); birds remained fat and testes were enlarged until the end (day 173) of the experiment. Locomotor activity also did not have a discernible pattern under the nongonadostimulatory photoregimes. Birds became active in the bright photophase (subjective day) of 12bl:12dl (10:2 lux) on day 5 (day 105 of the experiment), but beginning on day 113 more intense perch-hopping was initiated in the dim photophase (subjective night), indicating the appearance of nocturnal migratory restlessness in the caged birds. A 180 degrees transition in the bl:dl photophases at this time for 2 weeks resulted in complete shift in the timing of daytime and nighttime activity. This trend is maintained under all subsequent 12bl:12dl exposures. These results suggest that the light intensity required for photostimulation in the blackheaded bunting is absolute, and that the subjective interpretation of day and night depends upon the photophase contrast, as well.

Animals↗
PubMed1992

A characteristic cutaneous direct immunofluorescent pattern associated with Ro(SS-A) antibodies in subacute cutaneous lupus erythematosus.

BACKGROUND: Antibodies to Ro(SS-A) are present in most patients with subacute cutaneous lupus erythematosus (SCLE). Patients with SCLE also have cutaneous immune deposits. However, no correlation of Ro(SS-A) antibodies with immune deposits in skin biopsy specimens has been described. OBJECTIVE: The purpose of this study is to describe characteristic direct immunofluorescence (IF) findings in 32 patients and their association with serum antibodies and clinical diagnosis. METHODS: Serum from patients with characteristic cutaneous direct IF findings was examined for antinuclear antibodies by indirect IF and for antibodies to ribonucleoprotein, Sm, Ro(SS-A), and La(SS-B) by gel immunodiffusion. RESULTS: Twenty-two of 32 patients who exhibited discrete speckled IgG staining predominantly, but not exclusively, of the basal cell cytoplasm had SCLE. Ro(SS-A) antibodies were identified in 23 of 26 patients and Ro(SS-A) and/or La(SS-B) in 25 of 26 patients. CONCLUSION: Direct IF staining characterized by discrete speckled IgG deposits in the basal cell cytoplasm is associated with Ro(SS-A) antibodies and SCLE.

Acute Disease↗
PubMed1992

Studies on an Ostertagia ostertagi strain suspected to be resistant to benzimidazoles.

Four calves were infected with a susceptible (laboratory) strain of Ostertagia ostertagi and four with a field strain suspected to be resistant to benzimidazoles. After 25 days two calves from each group were treated with 3.5 mg kg-1 fenbendazole. Egg output fell to zero in all treated calves. Treated calves did not harbour worms at slaughter 35 days after infection. Significant differences between the strains were shown for ED50 values for thiabendazole in the egg hatch assay, but not in the tubulin binding assay. It is concluded that benzimidazole resistance in the suspected strain cannot be confirmed.

Animals↗
PubMed1992

Assessing Alzheimer severity with a global clinical scale.

Diagnosis of dementia needs to be complemented by precise determination of disease severity across the broad spectrum of disease progression. The Mini-Mental State Exam (MMS), the Activities-of-Daily-Living assessment (ADL) and the Clinical Dementia Rating scale (CDR) were modified for direct comparability and administered to 112 outpatients and 45 nursing home residents with a range of dementia severity from mild to profound. The scales showed the highest correlations for the probable Alzheimer's disease patient group (62) (Global Assessment of Dementia; GAD vs. ADL: r = 0.91; Extended Mini-Mental Assessment; EMA vs. GAD: r = 0.91; ADL vs. EMA: r = 0.86). For these patients, scores on the individual scales tended to be similar. Disparity among the three scores for individual cases was associated with the presence of comorbidities. The high correlations and correspondence among these scales demonstrate their reliability, validity, and utility in the assessment of dementia severity. The use of an average of these measures, with their increased precision, may give a more accurate indication of dementia severity over a broader range of impairment.

Activities of Daily Living↗
PubMed1992

Saccharomyces cerevisiae cells secreting an Aspergillus niger beta-galactosidase grow on whey permeate.

We describe the construction of a lactose-utilizing Saccharomyces cerevisiae that expresses the cDNA for a secreted, thermostable beta-galactosidase (lacA) from Aspergillus niger. Yeast cells expressing the lacA gene from the yeast ADH1 promotor on a multicopy plasmid secrete up to 40% of the total beta-galactosidase activity into the growth medium. The secreted product is extensively N-glycosylated, and cells expressing the lacA gene grow on whey permeate (4% w/v lactose) with a doubling time of 1.6 hours. Such strains may offer a solution to the increasing problem of waste whey disposal.

Alcohol Dehydrogenase↗
PubMed1992

Activation of B lymphocytes by NK cells.

The ability of NK cells to induce differentiation of B lymphocytes to IgM secretion in vitro has been investigated. Homogeneous preparations of NK cells obtained from IL-2 propagated splenocytes from SCID mice were found to have the ability to induce resting B lymphocytes to proliferate and secrete significant amounts of IgM. The induction is greatly enhanced by the presence of both IL-2 and IL-5 and does not require T lymphocytes or adherent cells in the responding population. Cell contact between the two populations is not necessary suggesting that the effect is mediated by soluble factor(s) which can be produced even by irradiated NK cells. Because the activity cannot be replaced by either r-tau-IFN or tumor necrosis factor-alpha or inhibited by antibodies to these lymphokines, a novel NK cell-derived factor(s) may be involved. The implications of this interaction between NK cells and B lymphocytes are discussed.

Animals↗
PubMed1992

Alzheimer Disease Assessment Scale: a subtest analysis.

The Alzheimer Disease Assessment Scale (ADAS) was administered to 61 Alzheimer patients, 52 elderly controls, and 80 controls between age 7 and 54 years. The Alzheimer group was categorized into different severity levels of dementia based on MMSE scores: very mild (> or = 24), mild (> or = 20), moderate (10-19), and severe (0-9). All 11 ADAS Cognitive subtest scores for the mild, moderate, and severe dementia groups were statistically worse than the elderly control group. This was also the case for the very mild group, except for Naming, Commands, Constructional Praxis, and Ideational Praxis. In terms of magnitude of effect, memory and spontaneous language items were the earliest indicators on the ADAS, while praxis, commands, and naming items were only sensitive later in the course of the disorder. The best single indicators of progression throughout the severity continuum of dementia (i.e., from normal to severe) were the Orientation subtest, the ADAS Cognitive score, and the ADAS Total score. The ADAS Noncognitive subtests generally did not show the progression with increasing dementia that was evident on the ADAS Cognitive subtest. Differences in educational level had no statistically significant effects on any of the ADAS subtest scores, and age differences were few and small in magnitude. The differential rate of decline of the various ADAS subtests appears to reflect both the changing pattern of cognitive impairments as a function of severity of DAT and also to some extent the psychometric limitations of some of the subtests.

Aged↗
PubMed1992

Differentiation of bullous pemphigoid from epidermolysis bullosa acquisita on frozen skin biopsies.

Patients with bullous pemphigoid and epidermolysis bullosa acquisita may have similar clinical, histologic, and routine immunohistologic features. These two diseases can be distinguished by routine diagnostic studies either on a patient's serum tested by indirect immunofluorescence on salt-split normal skin or by obtaining a fresh perilesional skin biopsy, inducing a split at the lamina lucida, and testing for the site of IgG deposition by direct immunofluorescence. Often the serum studies are negative, while direct immunofluorescent studies yield the characteristic linear IgG staining of the basement membrane zone. To eliminate the need for a repeat biopsy to make a laboratory differential diagnosis, we studied the efficacy of salt-splitting perilesional skin biopsies that had been previously submitted and frozen for routine direct immunofluorescent studies. The biopsies were thawed, salt-split, and processed for direct immunofluorescence. Three epidermolysis bullosa acquisita biopsies and seven bullous pemphigoid biopsies examined demonstrated IgG staining at sites consistent with their respective diagnoses. The IgG appeared in the dermal side of the split biopsies in epidermolysis bullosa acquisita and predominantly, or exclusively, in the epidermal side in bullous pemphigoid. Thus the direct immunofluorescent study of previously frozen and subsequently salt-split skin biopsies may be used for the differential diagnosis of bullous pemphigoid from epidermolysis bullosa acquisita. In most cases, it may eliminate the need for a repeat biopsy.

Basement Membrane↗
PubMed1992

A distinct stratum corneum antigen in psoriasis and its reactions with stratum corneum autoantibodies.

Stratum corneum antibodies are ubiquitous and can be detected by various immunological methods. Of these, the ones detected by hemagglutination undergo changes in antibody titers and have been implicated in psoriasis. The purpose of our study was to examine if differences exist in the activities of the antigens isolated from psoriatic scales in comparison to normal callus. Stratum corneum antigens were prepared by trypsin-phenol-water extraction. The water phase, which contains the stratum corneum antigen, was used to sensitize the red blood cells in the hemagglutination assay. The antibody activity in human sera was determined before and after absorption with antigens isolated from callus, psoriatic scales, and cell envelopes. We found notable differences in the antigens obtained from callus and psoriatic scales. These include higher antibody titers to the antigens of the scales, the presence of unique antigenic determinants on psoriatic scales and the localization of the antigen on cell envelopes. These immunological differences were corroborated by the marked biochemical differences of certain amino acids, most notably glycine and proline, and these differences were unique to psoriatic scales as they were not shared with other hyperproliferative disorders.

Amino Acids↗